1. Field of the Invention
The present invention relates to a roller device for controlling the unevenness of a sliver from a carding machine.
2. Description of Related Art
A carding machine with a device for controlling the unevenness of a sliver in a short cycle is known, where the device is arranged at a downstream side of a sliver delivery section of a card and is constructed as a set of a bottom and top measuring rollers, and a set of bottom and top drafting rollers. The measuring rollers are capable of being vertically displaced in relation to each other in accordance the thickness of a sliver passing between the rollers. Furthermore, a system is provided for controlling the rotational speed of the drafting rollers in accordance with the detected thickness of the sliver. As a result, a desired control of the drafting ratio (a ratio of the rotational speed of the drafting rollers with respect to the measuring rollers) is obtained, so as to obtain a sliver of a reduced unevenness. In the prior art, as shown in FIG. 7, one of the measuring rollers, for example, the top measuring roller is constructed as a roller with an annular groove, and the bottom measuring roller is constructed as a roller with a flange, which engages with the groove of the top measuring roller. Such a construction of the top and bottom measuring rollers is effective for preventing the sliver from being excessively widened at the measuring rollers, which is effective for reducing the unevenness at the measuring rollers.
However, in the prior art, the drafting rollers are a type with no flange and groove. In other words, the drafting rollers are constructed from a set of rollers of a flat surface. Such a flat construction of the drafting rollers causes an irregular drafting operation to be taken place, due to the fact that a widening of the sliver is not limited when it passes between the drafting rollers. Furthermore, in the prior art construction, foreign matter such as honeydews are apt to be attached to the surfaces of the measuring rollers and the drafting rollers, and a separate cleaning unit is necessary to clean these honeydews. Furthermore, in the prior art, in order to obtain a smooth threading of a sliver, a manual operation by an operator is essential so that the free end of the sliver is guided to the nip point of the drafting rollers.